Buzzing on Clips

When I captured some clips from my DV camera into Movie Maker and played them from collections, they sounded perfectly fine. When I put them into a time line, an annoying buzzing sound was added as well. When I exported the video, this buzzing sound did not disappear.

Also, in collections, I split apart some of the clips into different pieces and added these in different places in my documentary. Some of these clips buzz and some don't, even though they were shot together.

Does anyone know of a way to fix this? Does anyone have a similar problem?